In an image forming system in which a printing apparatus main body is attached with optional devices such as a post-processing device, an inserter device, and a paper feeding device, timing such as timing of transporting sheets to the optional devices is managed and controlled by the printing apparatus main body.
An example of the image forming system in which the optional device is attached to the printing apparatus main body is an image forming system shown in Japanese Unexamined Patent Publication No. 2003-21984 (Tokukai 2003-21984, published on Jan. 24, 2003). In this image forming system, an optional device in which a post-processing device and an inserter device are integrated is attached to an image forming apparatus main body. Here, when interleaving sheet insertion and staple processing are performed in the system, the optional devices are controlled in a unified manner by the image forming apparatus.
However, the system employing the optional device in which the post-processing device and the inserter device are integrated, as disclosed in Tokukai 2003-21984, offers less flexibility to a user who requires a function provided by the post-processing device (sort function, staple processing function, for example) but does not require a function provided by the inserter device (interleaving sheet insertion function).
Further, there is also an image forming system that includes the post-processing device and the inserter device separately as different optional devices and can serve as either a system composed of the image forming apparatus and the post-processing device or a system composed of the image forming apparatus, the post-processing device, and the inserter device. When the image forming system as described above is established as the system to which both the post-processing device and the inserter device are attached, the inserter device is provided between the image forming apparatus main body and the post-processing device.
In the system employing the optional device in which the post-processing device and the inserter device are integrated as described in Tokukai 2003-21984 (see FIG. 10(a)), and in the system composed of the image forming apparatus and the post-processing device (see FIG. 10(b)), only one system of a control line is required to connect the image forming apparatus with the optional device.
On the other hand, in the image forming system that includes the post-processing device and the inserter device separately as different optional devices as described above, the image forming apparatus main body manages and controls both the post-processing device and the inserter device. Accordingly, the image forming apparatus is required to use control lines in two systems, as shown in FIG. 10(c). This complicates the arrangement of the control system.
Further, in the image forming system provided with the inserter device, a transport path from the main body to the post-processing device is longer by the length of the inserter device, compared with the image forming system that is not provided with the inserter device. Accordingly, the image forming apparatus main body is required to prepare two types of control programs respectively for (i) control (timing control, in particular) of the post-processing device in a case where the inserter device is not attached, and (ii) control of the post-processing device in a case where the inserter device is attached. This increases the workload of control processing on the image forming apparatus.
Further, if the specification of the inserter device changes, for example, it is necessary to modify the control program of the image forming apparatus main body accordingly.